Ethylene polymers have been modified by the addition thereto of organo silanes for the purpose of providing compositions which have improved resistance to water-treeing and consequently improved electrical properties. For example, .gamma.-aminopropyltriethoxysilane has been added to polyethylene and the resultant composition suggested for use as insulation about electrical conductors, as described in German Offenlegungsschrift No. 2,727,430, published Feb. 22, 1979.
The addition of such amino substituted organo silanes to ethylene polymers for the purpose of improving electrical properties has not proved to be particularly effective. It has been found that these amino substituted organo silanes have a tendancy to volatilize from the insulation with an attendant loss of the ability of the insulation to resist water-treeing. Furthermore, such amino substituted organo silanes are disposed to the formation of gel specks in the insulation which, in turn, may serve as initiation points for water trees.